1. Field of the Invention
This invention relates generally to video signal processing and particularly to video signal processing systems and methods for converting an incoming video signal to an output having a standard NTSC 525-line interlaced or non-interlaced picture.
2. Description of the Prior Art
Video signals having 525, 675 and 875 horizontal scan lines are used in various commercial, industrial and military applications. Previous video signal processing circuitry is designed to operate with a single input horizontal scan line rate. Therefore, a video system designed for a 525 line rate is unusable with a 675 line signal.
Previous video scanners have the disadvantage of requiring storage of an entire picture sweep or more and require a relatively large amount of memory. A typical system must store at least as many lines as the lesser of the number of lines in the vertical sweep of the input or the output. For standard NTSC signals typical systems store at least 240 picture lines. The necessity of storing an entire picture sweep causes a delay of 6 to 24 msec between input and output signals. The delay between input and output signals is important in systems where the content of the picture is used to direct some action. The problem with the delay between input and output is analogous to driving an automobile while watching out the window what happened a second or so earlier.